Problem: $J$ $K$ $L$ If: $ JL = 21$, $ JK = 9x + 3$, and $ KL = 5x + 4$, Find $KL$.
Answer: From the diagram, we can see that the total length of ${JL}$ is the sum of ${JK}$ and ${KL}$ $ {JK} + {KL} = {JL}$ Substitute in the expressions that were given for each length: $ {9x + 3} + {5x + 4} = {21}$ Combine like terms: $ 14x + 7 = {21}$ Subtract $7$ from both sides: $ 14x = 14$ Divide both sides by $14$ to find $x$ $ x = 1$ Substitute $1$ for $x$ in the expression that was given for $KL$ $ KL = 5({1}) + 4$ Simplify: $ {KL = 5 + 4}$ Simplify to find ${KL}$ : $ {KL = 9}$